There are known three-way catalysts as exhaust gas purifying catalysts installed in vehicles and the like to oxidize or reduce harmful gas (hydrocarbon (HC), carbon monoxide (CO), nitrogen oxide (NOx)) contained in exhaust gas. In association with the recent increase in consciousness of environmental issues, regulations on exhaust gas emitted from vehicles and the like are being tightened. In response to such regulations, advances are being made in the improvement of three-way catalysts.
For example, there is disclosed a three-way catalyst as an exhaust gas purifying catalyst in which particles containing noble metal particles supported on a metal oxide are covered with a porous oxide (for example, refer to Japanese Patent Unexamined Publication No. 2008-284534). In this exhaust gas purifying catalyst, the metal oxide contains a rare earth element, alkali metal and alkaline-earth metal. Therefore, since the noble metal particles are prevented from moving from the metal oxide and being aggregated even under high temperature conditions, particle diameters of approximately several nanometers can be maintained.